Machine gun

ABSTRACT

The present invention relates to a firearm fired from an open bolt comprising a firing control mechanism  3  arranged below a frame inside which moving parts  2 , moved backward by gas recovery and forward by a return spring  12 , slide, the gas recovery and the return spring  12  being arranged below the axis of the barrel  5 , said firearm comprising a hammer  14  arranged, in the loaded position, above the axis of the barrel  5 , and the release of said hammer  14  being independent of the firing control mechanism  3.

SUBJECT OF THE INVENTION

The present invention relates to the percussion system of an open-boltfirearm.

PRIOR ART

For a machinegun firing with an open bolt or with an ammunition belt,the percussive energy is generally stored in the form of the potentialenergy of compression of the recoil spring, in the form of the kineticenergy of the moving parts, or in a spring precompressed between thestriker and the bolt.

Specifically, in the case of open-bolt operation, the shot is triggeredby the release of the moving parts, initially arranged in a rearwardposition, unlike the situation in a gun operating on a closed-boltprinciple, in which the shot is triggered by the release of a hammer bythe trigger blade, the moving parts being initially at rest, in aforward position, with the breech locked.

For example, in the case of the FN Minimi® machinegun, the striker isactuated by the forward movement of the moving parts after the breechhas been locked by the bolt.

Nevertheless, the percussion induced by the return movement of themoving parts has the disadvantage of being dependent on the efficiencyof the weapon operating cycle. Thus, when operating under harshconditions (sand, mud), the speed of the moving parts is slowed beforethe position in which the breech is closed is reached. The strikingenergy may then no longer be sufficient.

SUMMARY OF THE INVENTION

A first aspect of the invention relates to an open-bolt firearm,preferably a machinegun, comprising a fire-control mechanism arrangedunder a frame in which there slide moving parts which are moved rearwardby gas recovery and forward by a recoil spring, the gas recovery and therecoil spring being positioned under the axis of the barrel, saidfirearm comprising a hammer positioned, in the loaded position, abovethe axis of the barrel, and the release of said hammer being independentof the fire-control mechanism.

Preferably, the moving parts comprise a cam actuating release of thehammer during locking of the breech.

Advantageously, a sear is arranged in such a way as to control releaseof the hammer when the cam moves said sear.

Preferably, the hammer comprises a concave sliding surface directedtoward the moving parts.

Advantageously, the slide comprises at its lower rear end a cam arrangedin such a way as to bear on in the vicinity of the lower end of thesliding surface during a first section of the recoil of the slide.

Preferably, the slide comprises at its upper rear end a cam arranged insuch a way as to bear on the sliding surface during a second section ofthe recoil of the slide.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 depicts an overall view of a machinegun according to theinvention, with the frame not depicted, so as to be able to see thevarious elements of the mechanism.

FIG. 2 depicts a view of a detail of the device of FIG. 1, showing thevarious components of the mechanism of the invention, upon release ofthe moving parts.

FIG. 3 depicts a detailed view of the mechanism of FIG. 1, during theforward movement of the moving parts.

FIG. 4 depicts a detailed view of the mechanism of FIG. 1, after thelocking of the breech.

FIG. 5 depicts a detailed view of the mechanism of FIG. 1, just afterthe percussion.

FIG. 6 depicts a detailed view of the mechanism of FIG. 1, during therearward return of the moving parts (intermediate position 1).

FIG. 7 depicts a detailed view of the mechanism of FIG. 1, during therearward return of the moving parts (intermediate position 2).

REFERENCES IN THE FIGURES

-   -   1. Hammer mechanism    -   2. Moving parts    -   3. Trigger mechanism (incorporated into the trigger guard)    -   4. Chamber    -   5. Barrel    -   6. Butt    -   7. Slide (sometimes also referred to as sliding block)    -   8. Bolt    -   9. Second hammer reloading cam    -   10. Hammer sear release cam    -   11. First hammer reloading cam    -   12. Recoil spring    -   13. Hammer sear    -   14. Hammer    -   15. Concave sliding surface    -   16. Hammer spring    -   17. Extension of the gas recovery piston    -   18. First point of reloading contact between slide and hammer    -   19. Second point of reloading contact between slide and hammer    -   20. Firing pin

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a hammer mechanism 1 designed forfirearms firing from an open bolt, in automatic or semiautomatic mode.In such a weapon, belt-fed loading from the top of the frame forces thedesigner to position the gas recovery and the recoil spring below theaxis of the barrel 5 rather than above same.

The consequence of this positioning is that it is difficult to site ahammer mechanism incorporated into the trigger guard, as the latter isseparated from the firing pin by the recoil spring and the bottom of themoving parts in the continuation of the gas recovery piston.

The present invention makes use of the fact that during open-boltoperation, initiation of firing (the start of the cycle) is associatednot with the striking of a cartridge in the chamber 4 but with therelease of the moving parts 2. That being the case, there is no longerany need to incorporate the hammer mechanism into the trigger guard, inmechanical connection with the trigger mechanism.

Rather, in the present invention, the release of the hammer 14 iscontrolled entirely by the movement of the slide 7, which ensuresoptimal synchronization between the locking of the breech by the bolt 8and the percussion.

Because the hammer mechanism 1 is no longer connected with the triggermechanism 3, it is then possible to position the hammer mechanism 1above the axis of the barrel rather than below this axis.

FIG. 1 shows one example of a machinegun according to the invention,without the frame, in order to show the elements thereof. It shows ahammer mechanism 1 positioned above the axis of the barrel 5 andoperating entirely autonomously. In particular, no mechanism connectsthe hammer mechanism 1 with the trigger mechanism 3.

FIGS. 2 to 7 show detailed views of the various elements of thepercussion mechanism during a cycle of the machinegun. In FIG. 1, themoving parts are at rest awaiting firing. In that position, the hammermechanism 1 is practically out of the path of the slide 7 and allowssame to move freely forward, as depicted in FIG. 3.

FIG. 4 shows the end of the forward movement of the slide 7, at themoment of locking. At that moment, the cam 10 pushes the sear 13forward, and this releases the hammer 14, which begins to rotate aboutits axis under the effect of the hammer spring 16.

FIG. 5 depicts the first few moments after percussion, at the start ofthe recoil of the moving parts 2. At this moment, as the slide 7 isrecoiling, the cam 11 pushes on the sliding surface 15 beginning tocompress the hammer spring. Note that the point 18 of contact betweenthe slide 7 and the hammer 14 is as far away as possible from the axisof rotation of the hammer, so as to reduce the impact experienced by thehammer 14, and therefore the wearing and fatigue thereof, thus reducingthe risk of breakage in the long term. The presence of the rounded cam11 allows wear and fatigue to be reduced still further.

FIG. 6 depicts the continuation of the cycle, with the moving parts in afirst intermediate position. Here it may be seen that the firing pin iseffaced from the slide 7. In this recoil phase, the bolt 4 still remainsattached to the chamber 4 while the slide 7 is already recoilingrearward.

FIG. 7 depicts the continuation of the cycle, the moving parts 2 beingin a second intermediate position. In this position, the slide 7 pusheson the sliding surface via a second cam 9 this time arranged in theupper part of the slide. This is because, in this position, the distancebetween the axis of the hammer and the cam 9 is great enough for theacceleration of the hammer to be limited.

The hammer lifting dynamics are optimized by the adoption of a slidingsurface 15 of the hammer in contact with the slide 7, which is concave.This is because this shape, combined with the presence of a cam 11 inthe lower part of the rear of the slide 7, allows contact to be madefirst of all on a surface of the slide opposite the position of thehammer, thereby increasing the lifting lever arm and reducing the impactassociated therewith. The curvature of this surface, with no sharpangles, also makes this movement more continuous and avoids impacts thatcould lead to material fatigue.

The end of the hammer lifting movement is brought about by a cam 9situated on the upper surface of the slide 7. This cam 9 is set backwith respect to the lower cam 11, so that the cam 11 acts at the startof the lift and the cam 9 at the end of the lift.

Note that the positioning of the hammer mechanism in the upper part ofthe weapon not only makes it possible to get around the problem of thebulkiness of the recoil spring and of the moving parts in the case oftop loading, but also makes it possible to reduce the bulkiness of thetrigger guard, allowing for a more compact design of the trigger guard.

1. An open-bolt firearm comprising a fire-control mechanism arrangedunder a frame in which there slide moving parts which are moved rearwardby a gas recovery piston and forward by a recoil spring, the gasrecovery piston and the recoil spring being positioned under an axis ofthe barrel, said firearm comprising a hammer positioned, in a loadedposition, above the axis of the barrel, and release of said hammer beingindependent of the fire-control mechanism.
 2. The firearm as claimed inclaim 1, wherein the moving parts comprise a cam actuating the releaseof the hammer during locking of a bolt.
 3. The firearm as claimed inclaim 2, comprising a sear configured to control the release of thehammer when the cam moves said sear.
 4. The firearm as claimed in claim1, wherein the hammer comprises a concave sliding surface directedtoward the moving parts.
 5. The firearm as claimed in claim 4, furthercomprising a slide having at its lower rear end an upper cam configuredto bear on the lower end of the concave sliding surface during a firstsection of a recoil of the slide.
 6. The firearm as claimed in claim 5,wherein the slide comprises at its upper rear end a lower cam configuredto bear on the concave sliding surface during a second section of therecoil of the slide.